The present invention concerns a monolithic integrated digital-to-analog converter in which resistances and switches are represented by insulated-gate field-effect transistors. Reference is made to the periodical "Funk-Technik" 30, No. 8, 1975, pp. 217 to 219.
German Pat. No. 2,059,933 teaches use of insulated-gate field-effect transistors whose resistance values are determined by a fixed ratio of channel width to channel length for the resistances in MOS digital-to-analog converters.
The invention relates to a monolithic integrated circuit for a digital-to-analog converter of such a type.
When such monolithic integrated circuits are mass-produced by separating semiconductor wafers into chips containing the individual circuits, a problem arises. The output signals of the converters vary as a result of manufacturing conditions, which may lead to considerable variations in yield. It has been found that variations over a single wafer are a minor problem, while those over a plurality of wafers may be considerable.